Rheostat



April 19 1927.

E. H. BOBO RHEOSTAT Filed A'ug. 21, 1925 2 Sheets-#Sheet 1 BY ya;

ATTORNEYS April 19,1927. I

E. H. BOBO RHEOSTAT Filed Aug. 21. 1925 2 Sheets-Sheet 2 Y my@ w Mmm. AQ/\ f A m m w Bmw m Nm. @nw www1 @Nl N m @N N NNK Hl. m... W @W .0. 1w NJ INVENTOR Ef/9. 5060,

ATTORNEYS Patented Apr. ie; 1927.

UNITED STATES iiizaiozin EDWARD HALFORD BOBO, OF RANGER, TEXAS.

Application lcd August 21, 1925. Serial No. 51,623.

l This invention relates to improvements in 'rheostats The prime purpose of this invention is to provide a filament rheostat for electron tubes which will permit varyingthe current flow through aiilament in an exceedingly even and uniform manner.

' Other objects will hereinafter appear.

I accomplish my invention by' the provision of a rheostat structure wherein mercury or other current conductive liquid serves as a current connecting medium between a resistance coil and a conductor. `Means are provided whereby the mercury is caused to move and during said movement either increase or decrease the amount of the resistance coil connected in the circuit controlled thereby.

The present invention is illustrated by way of example in theaccoinpanying drawings, in which: f

Figure 1 is a rear elevation of a rheostat constructed in accordance with the present` invention, v

Figure 2 is a side elevation of the same,

Figure 3 is a view similar to Figure 1 with parts broken away and shown in section in order to more clearly illustrate the invention, and Y Figure 4 is a vertical sectional view taken substantially on the line 4--4 of Figure 1.

Referring 'to the drawings in detail, 10 indicates a support plate and 11 a U-shaped l frame member which maybe secured to the plate 1() by screws 12. A hollow shaft 13 has its one end journaled in plate lOand l its other end reduced as at 14, and this reduced end1 journaled in the bridge portion of the U-shaped frame member 11. A bolt or rod 15 is tightly fitted into the hollow shaft 13, one end of said bolt extending from the shaft and carrying a knob 16. The shaft 13 has molded thereon a sleeve 17 which is of insulating material and which has embedded therein a current conductor bar 18'. A spring washer 18 is' interposed between the sleeve 17 and plate 10. A collar 19 is arranged upon the shaft 13 and interposed between the sleeve 17 and frame `member 11. A set screw 20 is employed to secure x together the collar 19, shaft 13 and rod .15. The collar 19 is formed with arms 21`which support at their outer ends an arcuate shaped tube generally indicated by the reference the core 24 is formed with a`fhead`25 which basan extension 26. The end of tube 22 having a cap 23 is shaped to fit tightly about the head 25 of vcore 24. The cap 23 is prodate the head extension 26.

The core 24 is formed with a longitudinally extending groove27 which begins Yat the vided with a central opening to accommo khead 24 and terminates with the opposite lend of the core.

The core has embedded therein a resistance coil 2,8. The coil is preferably tinned and a portion of each convolution of said coil is disposed in the slot 27 as illustrated to advantage in Figures 3 and 4. The one end of the coil 28 is bent to engage the bottom of groove 27 as shown at 29, Fig. y3. The remaining end of coil is connected to one end of the conductor bar 18. The other end of conductor bar 18 is connected to the inner end of a spiral spring 31, said spiral spring encircling the sleeve 17 on shaft 13 and having its outer end suitably secured to a screw 33 carried by the plate 10. The screw 33 carries a nut 34 to permit a circuit terminal to be connectedY therewith. lt should be noted that the plate 10 is ofy current insulating material while n the frame member 11 is of current conducting material. e

The reduced end 140i shaft 13 has electrically connected thereto the inner end of a spiral spring 35, said sprin having its outer end disposed in a slotte head 36 of a pin 37. The last named end of spring 35 should be soldered to in 37. Also the inner end of said spring s ould be solderedl to shaft 13. Soldered connections should also be made between the ends of spiral sprin 31 and the bar 18 and screw 33. The pin 3% is suited to permit a circuit terminal to bev connected-therewith. Also it will be noted that pin 37 is disposed in the path of cap 23 and said pin serves as a stop to `limit rotative movement of the tube 22.

Within the tube 22 there is placed a small quantity of mercury and the remaining space of the tube is :filled with a non-oxidizing gas such as nitrogen. The capped end of tube 22 should be tightly sealed and this can be accomplished by shellaclring the head 25 of core 2li. It should be here pointed out that the quantity of mercury should be sucient to serve as a connecting medium between the tube 22 and the resistance coil 28 as long as the tube 22 is not rotated to a position to bringl the mercury into the end of tube entenf'ng from the free end of core 24;. rllhe space occurring between the tree end of core 24 and the associated end of tube 22 provides a chamber e0 which is ci' suiiicient capacity to hold the quantity of mercury necessary in tube 22 for the operation o the device.

In the use of the present device, the terminals 33 and 37 may be connected with a filament circuitot an electron tube in the usual manner, and ii the tube is rotad to a position shown in the different gures of the drawings, the mercury therein will electrically connect the central portion of resistance coil 28 to the tube 22. The current will then flow through spiral 3l, bar 18, resistance 28, and from thence through body of mercury to tube 22. The current is conducted from tube 22 through arms 2l and through spiral spring to terminal pin 37. In the instance above described, about one halt of the resistance coil is included in the circuit being controlled. If the tube 22 is rotated to cause the mercury to move by gravity toward chamber 40, more resistance will be continually inserted into the filament circuit in an obvious manner; and if the tube 22 is rotated in the opposite direction the resistance in the lament circuit will be radually decreased. When the tube 22 is eing rotated to decrease the resistance of coil 28, said resistance will be entirel eliminated from the filament circuit w en the cap 23 engages sto 37. The current now can flow from con uctor bar 18 to terminal or stop 37, and thus not pass through any' part of resistance 28. In case the tube 22 is rotated until the mercury is in chamber 40 then the filament circuit will be open. The tube 22 can be brought to the last named position when it is desired to disconnect the lament circuit being controlled from its source of supply.

While I have described my invention as being particularly applicable for control- -ling filament circuits of electron tube, it is to be understood I am aware of the fact that the same vmay be used for other purposes, and I am not to be limited to the use described.

I claim:

1. In a rheostat, an arcuate shaped metallic tube, means for rotating'the tube about its axis, a core of insulating material arranged in said tube, a resistance coil molded withinvsaid core with a part of each convolution of said resistance exposed, and a body of current conducting liquid in the tube adapted to move with rotation of the tube and during said movement change the point of electrical connection between the tube and resistance coil in a continuous manner. A

2. In a rheostat, an arcuate shaped metallic tube, means whereby the tube may be rotated about its axis, a core of insulating material in the tube said core having a longitudinal groove, a resistance coil embedded in the core longitudinally thereof, and each convolution of the coil having a portion disposed in said groove, and a body of current conducting liquid in the tube adapted to move with rotation of the tube and during said movement change the point of electrical contact between the tube and resistance in a continuous manner.

3. A rheostat comprising a rotatable metallic sealed tube, a resistance arranged longitudinally within the tube and insulated therefrom, a body of mercury within the tube adapted to establish a single point of contact between the tube and resistance and change the point of said contact with the rotation of said tube, and a non-oxidizing gas within the tube.

4. A rheostat comprising a metallic tube arcuate in shape and one end closed, means for rotating the tube about its axis, a core of insulating material tightly tted within the tube and closing the open end of the tube, said core having an elongated groove with a resistance wire therein, and a body of current conducting li uid within the tube andadapted to move within the groove.

5. A rheostat comprising a metallic tube arcuate in shape and one end closed, means for rotating the tube about its axis, a core of insulating material tightly tted within the tube and closing the open end of the tube, said core having a longitudinal groove and its end associated with the closed end of .tube being spaced therefrom, a resistance wire disposed in the cove, and a body of current conducting liquid within the tube and adapted to move within the groove and also to iow or move intothe space between the closed end of tube and associated end of vcore when the tube is rotated to bring the closed end thereof lowermost.

6. A rheostat comprising a metallic tube arcuate in shape and one end closed, means for rotating the tube about its axis, a core of insulating material tightly vfitted within the tubeand closin the open end of the tube, a resistance' wire carrled bythe core and having its one end extending through the last named end of the core to serve as a terminahand a bo'dy of current conducting liquid Within the tube adapted; to establish cein-cuate in shape and one end closed, means for rotating the tube about its axis? e eoe of iusuating material tightly iitted 'Within 'the tube and closing thek open end of the tube, said core having a longitudinal groove,

a esistanee wire molded within the @ore lo and sections thuereol exposed in seid groove., and `e body of current conducting liquid Within the tube and adapted to move Within the groove., Y

EDWARD HALFORU BOB@ 

